The present invention relates to an instrument cluster having a printed circuit board on which a light source is provided in order to generate light for illuminating a display, and a frame in which the printed circuit board is held.
Such instrument clusters that are fitted in the dashboard of a vehicle in the visual range of the driver are known from motor vehicles. As a rule, they have a multiplicity of display panels that are accommodated in a common plastic housing and can be read off by the driver through a transparent cover. These instrument clusters provide both digital and analog display panels that display to the driver multifarious information such as, for example, vehicle speed, engine speed or tank filling level.
All the display panels share in common a dial with numerals or symbols that is arranged on the display panel and bears the luminous symbols required for identification. As a rule, the dial is a separate disk made from nonluminous material and to which an appropriate imprint for the individual variables to be displayed is applied. The display panels are arranged spaced apart in a defined fashion on a printed circuit board having a circuit arrangement and light-emitting light sources, and are surrounded by a frame having a transparent pane. The arrangement and number of the display panels to be used are determined by the number and position of the light sources to be arranged on the printed circuit board.
It is customary for this purpose to distribute the light sources behind the entire surface to be illuminated in order to ensure that the luminosity and luminance distribution of the display panels are as uniform as possible. Economizing with reference to the number of light-emitting light sources requires the use of particular light guides having light channels that, for example, guide the emitted light along a longitudinal direction and backlight the scale marks, for example, of a dial to be illuminated. As a rule, the size of the printed circuit board corresponds to the area of the display panels to be illuminated and consequently entails a high price and high manufacturing costs.
U.S. Pat. No. 6,499,852 B1 discloses for an instrument cluster an illuminating device in which a number of light sources are arranged on a printed circuit board. The printed circuit board is arranged on the outer circumference of the display panel, and the light sources are distributed along the circumference of the display panel. A reflector that is arranged along the outer circumference of the display panel reflects the light of the light sources in the direction of the middle of the display panel.
FR 2761029 A1 discloses for a motor vehicle an instrument cluster in which the display panel is formed by a plate that is designed as a light guide. A light source arranged on a printed circuit board radiates light into a light guide that is designed such that the light is deflected and coupled into the display panel.
DE 19800389 A1 discloses a dashboard that is illuminated from the front side and comprises a printed circuit board onto which conductor tracks are printed on a side pointing backward, and to which there is applied serigraphically on a side pointing forward a layer that permits the recognition of display marks, in particular the scale of a dial. The printed circuit board is fastened in a frame in which there is formed a slot in which there are arranged illuminating means that illuminate the dial from the front side. The supply of the illuminating means is performed with the aid of a flexible, compliant circuit.